This invention relates to an improvement in the design of the xe2x80x9cmultiposition self-locking gripperxe2x80x9d. The Multiposition self-locking gripper is an important discovery that allows a gripping or clamping mechanism to close and lock on objects of varying sizes. However, by incorporating the self locking mechanism into the operating space of a cylinder, it was discovered that the principal of the Multiposftion self-locking cylinder could indeed be applied to the entire product line. It was further discovered that this xe2x80x9cMultiposition Force Locking Cylinderxe2x80x9d could be used as a motor mechanism on numerous mechanical devices requiring self locking principles.
A cylinder is defined as a motor device, and is frequently composed of a piston, moving rod, and a substantially cylindrical containment. The containment and the piston normally include seals and bearing surfaces. A cylinder must be operated by the input of a fluid substance. The two most frequently used fluids are air and oil. Air cylinders are very inexpensive and relatively maintenance free.
For many years product and machinery users have been searching for a cylinder that would allow them to close/open and lock on parts of various sizes. Fluid power specialists designed fluid devices with check valves to inhibit the release of a fluid. However, pneumatic fluid remains compressible and, therefore, does not lock the motion of the cylinder. Hydraulic devices would eventually release the high pressure fluid into a low pressure containment and the mechanical force of the cylinder device would reduce to zero. Heat, high force and long periods of time would cause these devices to release the payload object.
Mechanisms that incorporated a cylinder with a braking device have been available on the market. However, after braking, the braking device must be released to again move the cylinder. The release operation required mechanical input from a second motor means, making the braking mechanism expensive and impractical for many applications.
The Multiposition Force Locking Cylinder will close and hold a payload regardless of the opposing force. The nature of the multiposition force locking cylinder is such that any increase in the opposing force results in an equal but opposite locking force. This remains true up until the structural failure of the physical parts of the cylinder. The Multiposition Force Locking Cylinder will remain locked regardless of the reason for failure (external to the locking mechanism). The Multiposition Force Locking Cylinder depends only on its own internal locking mechanisms. Fluid power failure will not cause the Multiposition Force Locking Cylinder to release.
The Multiposition Force Locking Cylinder is an important safety improvement. The simple, self locking principal now allows engineers and designers to offer safe pneumatic systems to their customers.
Most cylinder mechanisms have a direct physical contact between the piston means and the movable rod device, resulting in a direct input to output status. Since the primary function of the piston and rod in a conventional cylinder is to provide motion and exert force, locking must be achieved by the introduction of a second independents operating mechanism, typically a check valve or a rod locking clamp mechanism. Unfortunately, a check valve does not accurately and completely lock a pneumatic cylinder. Gaseous fluids are all compressible and obey the PV=NRT gas law. Additional forces will compress the fluid further resulting in motion of the piston and rod subassembly. A rod locking clamp mechanism is an effective way to lock the piston and rod subassembly. Unfortunately, these devices are expensive to build and often result in critical wear on the rod surface.
The invention disclosed overcomes many problems associated with the prior art by providing a force locking cylinder that achieves a true self-locking mode, independent of external media inputs. This unique mechanism is capable of locking at any position along the cylinder stroke path. The invention comprises generally one or more movable rod devices, a number of spherical or cylindrical locking devices, a release sleeve, a locking sleeve which is built into a piston subassembly, a lock rod, and structural members including a cylinder, end caps, seals and bearings. Therefore, the cylinder resembles a conventional fluid power cylinder.
This invention takes advantage of forces that are naturally generated during the operation of an air cylinder to lock and unlock the cylinder rod. At the same time, this invention utilizes these same forces to control the distance that the cylinder rod will move prior to locking. Opposing force, alone, is the primary method for controlling the distance that the cylinder rod will move. Opposing force is generated when an extending (or retracting) cylinder encounters an object that will not move. High mass, high velocity, acceleration, or static forces are each methods of the generating an opposing force. When an opposing force is encountered the cylinder rod stops its motion.
A truly unique relationship between the piston, moveable rod, and lock rod was invented to achieve the lock and release capability. The piston means and the cylinder rod subassembly are not rigidly attached in this invention. A small translational distance between the piston means and the cylinder rod subassembly allows the cylinder rod subassembly and adjacent components to move within the piston subassembly 143. This small translation results in additional control over two or more functions without the addition of a second degree of freedom. The piston means continues moving which results in the locking of the cylinder rod to the lock rod. A single piston and release subassembly 124 can achieve (1) movement, (2) locking and (3) unlocking of the cylinder rod 135.
Due to the unique, two phase operation of the piston means, it is possible to move the cylinder rod through a random distance against the payload object. The distance is generally controlled by the force generated against a payload object.
Close-to-Lockxe2x80x94Moving a cylinder rod to a retracted position where the rod is locked rigidly in place.
End Effectorxe2x80x94A functional devise designed to achieve a task while attached to a motion mechanism.
Force Track Meansxe2x80x94A device capable of exerting forces over a displacement distance. Specific examples are a ball bearing, a thrust bearing, a linear guide, and a roller guide.
Gripperxe2x80x94A mechanism designed to exert force and hold a payload object.
Lockingxe2x80x94The task when a cylinder encounters a resisting force that substantially stops motion of the rod and activates a mechanism.
Motor Meansxe2x80x94A motion output devise capable of converting energy inputs into linear or rotary motion of a specific mass.
Open-to-Lockxe2x80x94Moving a cylinders rod to an extended position where ft is locked rigidly in place.
Payload Forcexe2x80x94The force exerted on an cylinder by a payload object due to weight, size, mass, or acceleration.
Payload Objectxe2x80x94The workpiece or target object.
Random Distancexe2x80x94A translation that can vary from one operating cycle to the next operating cycle.
Releasingxe2x80x94The task when a cylinder terminates all forces against a payload object.
Self-Lockingxe2x80x94A mechanism will close (open) and hold the payload object regardless of the force and regardless of the reason for failure (external to the mechanism).
Extendxe2x80x94the motion of the cylinder rod out away from the cylinder body.
Retractxe2x80x94the motion of the cylinder or rod into the cylinder body.
Cylinderxe2x80x94a pneumatic devise comprised of a piston, rod, and caps and a sleeve, along with numerous seals and bearings.
Rod (or cylinder rod)xe2x80x94a mechanical devise designed to transmit linear forces from a fluid power device to a payload object.
End capsxe2x80x94A mechanical devise designed to contain the sleeve on an air cylinder. Two end caps are used with a sleeve to define the cylinder operating space. One end cap has a central space to accommodate the cylinder rod.